1. Field of the Invention
The present invention relates to printout by a multi-head printer, such as a two-head ink jet printer, in which resolution for each of the print heads is controlled independently.
2. Description of the Related Art
Conventional printers such a single head ink jet printers are capable of printing successive pages in differing resolutions. Specifically, commencing with initiation of printout for each page, it is possible to specify a print resolution such as a low print resolution (e.g., 360 dpixc3x97360 dpi) or a higher resolution (e.g., 720 dpixc3x97720 dpi or 720 dpixc3x971440 dpi). As a consequence, it is possible to print print information for one page with a first resolution, and print print information for a succeeding page at a different resolution.
Print information for any one page is often a mixture of some information that is preferably printed at a high resolution, together with other information that need not necessarily be printed at high resolution. For example, print information for one page might consist of text information for which a lower resolution is sufficient, together with non-text information such as images or line drawings for which a higher resolution is preferable. Because conventional systems are only able to print each page at a single resolution, however, such mixed information must be printed at the higher resolution which results in reduced efficiency when printing the page information for which reduced resolution is adequate.
Recently-proposed printers include more than one print head, such as two or more print heads. Exemplary systems are described in application Ser. No. 08/901,719, xe2x80x9cPrint Driver For A Color Printerxe2x80x9d; and application Ser. No. 08/901,560, xe2x80x9cAuto-Alignment System For A Printing Devicexe2x80x9d, both of which are assigned in common with the instant application and which are incorporated herein by reference as if set forth in full. The referenced applications describe an ink jet printer which includes two print heads, with information printed by each print head being commanded from a host computer. Printers with multiple print heads provide significant increases in printing efficiencies. However, to the knowledge of the inventors herein, no previous consideration has been given to increasing print efficiency when printing the mixed print data described above.
It is an object of the invention to increase print efficiency of a printer having multiple print heads by controlling resolution for each print head independently.
Thus, in one aspect, which is applicable to a printer having at least first and second print heads, the invention controls print resolution of the first and second print heads independently of each other. Where the print heads are ink jet print heads which eject ink droplets based on digital data stored in a print buffer, resolution is controlled by controlling ink droplet size and by controlling readout order from the print buffer, with droplet size and readout order being controlled independently for each print head. The resolution to which each print head is controlled may be determined manually by a user or may be determined automatically by a host computer. Automatic determination of print head resolution is preferably made based on relative configuration of the print heads (for example, whether the print heads are the same or different), based on content of print data, and based on type of print media.
Because resolution of each print head is controlled independently, it is possible to increase print efficiency in situations where print information for one page is mixed between some print information for which a high resolution is desirable, and other print information for which a lower resolution is adequate. In such circumstances, one print head is controlled to print at a high resolution, and another print head is controlled to print at a lower resolution. Each print head then prints the print information with matching print resolution characteristics, thereby speeding the overall printing process.
In other aspects, the invention is a printer having at least first and second print heads with each print head having an independently controllable print resolution. The printer is adapted to receive commands for setting print resolution for each print head independently, and to effect printout in accordance with the commanded resolution.
In particularly preferred forms, the printer includes print heads whose configurations differ, such as a first print head adapted to provide high resolution color images, and a second print head adapted to print monotone (such as black) images but across a print band that is wider than the first print head. In this configuration, the first print head is commanded to print at a high resolution for non-text images, whereas the second print head is commanded to print at a lower print resolution for text images. Where the print heads are comprised by ink jet print heads which eject ink droplets based on digital data in a print buffer, resolution is changed by commanding different ink droplet sizes and by commanding different readout order for the digital data in each print buffer.
Other aspects of the invention include a user interface that allows a user to designate print resolution for print information of one page that includes text print data mixed with non-text print data. The user interface permits the user to designate a resolution for the text that differs from the resolution for the non-text.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.